They are great but pricey... I moved the apartment not long ago and had to terminate my Salt Fibre contract as my building has also XGS-PON and Salt and UPC do not support it.
I considered Init7 but ended up with Yallo Fibre. They support XGS-PON service is great so far and I pay 34 CHF/month. Ask them for an offer using their, they speak English and waived the installation fee